The obstructive sleep apnea syndrome (OSAS) is a sleep disorder in which the patient exhibits breathing pauses during sleep, resulting in excessive daytime sleepiness, sleep fragmentation, and intermittent hypoxia. Patients suffering from the disorder have a greater risk of developing diurnal hypertension, myocardial infarction, ventricular failure, pulmonary hypertension, cardiac dysrhythmias and stroke. In addition to health problems, OSAS significantly reduces the effectiveness and alertness of the individual during the day which adversely effects the individual's lifestyle and increases the risk of injury to the individual and others from motor vehicle and work-related accidents.
OSAS is typically diagnosed by polysomnographic testing. This procedure involves monitoring the patient overnight to record brain activity, eye movements, chin and leg muscle movements, cardiac rhythm, snoring intensity, oronasal airflow, respiratory muscle effort, and blood oxygen saturation. The test is time consuming, labor intensive and expensive. Thus, a method of screening patients to reliably determine whether or not they may be at risk for OSAS reduces the number of patients who are unnecessarily subjected to polysomnographic testing. More importantly, earlier diagnosis and treatment of OSAS would be promoted because the screening results would eliminate the reluctance of a physician to prescribe polysomnographic testing for those patients who do not exhibit dramatic OSAS symptoms.
Mathematical formulas have been developed to clinically predict whether a patient is likely to suffer from OSAS. These mathematical models primarily rely on measurements of body mass index and neck circumference, two factors which are indicative of the obesity of the patient. Obesity is one of the important risk factors for OSAS. However, not all patients who suffer from OSAS are obese. Although prior mathematical models have combined the body mass index and neck circumference measurements with oxygen saturation levels, witnessed apneas and questionnaire data, these mathematical models are of little use in screening patients who are not obese. A system of screening patients without relying on whether or not they are obese would ensure that further testing is prescribed for all patients at risk for OSAS independent of their body weight.
Another significant risk factor in the development of OSAS is craniofacial dysmorphism (disproportionate craniofacial anatomy). Abnormalities associated with craniofacial dysmorphism include a reduction in the upper airway caliber which makes the airway susceptible to collapse during sleep. Abnormalities in craniomandibular morphology, such as a narrow or posteriorly displaced mandible, are often found in OSAS patients. Another abnormality commonly found in OSAS patients is a highly arched palate. A system of quickly and accurately detecting the presence of a narrow or posteriorly displaced mandible and/or a highly arched palate would facilitate the assessment of a patient's OSAS risk.